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javaoopclassinheritancepolymorphism

Accessing private instance variables of parent from child class?

Let's say we have a class foo which has a private instance variable bar.

Now let us have another class, baz, which extends foo. Can non-static methods in baz access foo's variable bar if there is no accessor method defined in foo?

I'm working in Java, by the way.

Solution

  • No, not according to the java language specification, 3rd edition:

    6.6.8 Example: private Fields, Methods, and Constructors

    A private class member or constructor is accessible only within the body of the top level class (§7.6) that encloses the declaration of the member or constructor. It is not inherited by subclasses.

    But regardless of this language restriction, you can access private fields through reflection:

    Field privateStringField = 
   MyClass.class.getDeclaredField("privateString");
privateStringField.setAccessible(true);

String fieldValue = (String) privateStringField.get(privateObject);
System.out.println("fieldValue = " + fieldValue);